Military doctrine

In general, there are four levels of abstraction of military doctrine, the highest level not limited to military means but including all national ways to affect behavior. While terms such as strategy go back to antiquity, the modern usage of these levels starts from Carl von Clausewitz's definition of strategy, with variations on how it is translated from the German, as "the extension of national politics by military means". In modern international usage, additional refinements are needed to deal with non-state actors, sometimes more in combat terms but also in lower-intensity efforts, including peacekeeping, peace enforcement, and nation building. There are also military doctrines, typically for national or multinational organizations, that address the various levels in specific contexts, such as insurgency or air warfare planning.

For centuries, there was, at best, a distinction between strategy and tactics. They used Clausewitz's definition of strategy to define the objectives to start a conflict, and a generic discussion of tactics as how the battles would be fought. Battles, of course, differ in the type of units and rules of engagement, for which there are doctrines. A doctrine for a naval blockade will be very different from a doctrine for light infantry in high-altitude mountain warfare.

In World War II, strategy was at the level of theaters of operations, operational art was at the level of ground units from army group to corps, and naval units at the fleet level; tactics were from division to fire team. The current trend, however, is for militaries with advanced technology to use smaller units at the various levels.

There are levels of abstraction above and below strategy, and the definition of strategy itself has evolved. The main levels are:

Level	Objectives	Types of units involved
Grand strategy	Deciding the full range of national policy toward other actors	Military as a whole, diplomacy, international economic policy, psychological operations, international law enforcement
Strategy	Determining the composition of the military and its deployment; high-level regional objectives in war	Geographic theaters of operations, field army and larger units on land, special operations forces under high-level command, long-range aviation and missiles, sea control and major naval operations
Operational art	Preparing for battle within a geographic or other large scope, and creating the opportunities to engage in battle on favorable terms	Ground troops traditionally at corps size (i.e., 25,000 to 75,000 conventional soldiers), but in highly technological militaries, down to brigade equivalent. Air forces directed as a theater or campaign resource.
Tactics	How battles are fought once begun, or the methods and objectives of quick strikes	Ground troops from fire team (3-5 soldiers) to division (up to 25,000 soldiers)

Grand strategy

Grand strategy includes, but is not limited to, military means, but also diplomacy, economic measures, covert operations, law enforcement, intelligence collection and analysis, psychological operations, etc.

Strategy

Strategy is still considered associated with using military means to influence behavior of other actors, but the term "grand strategy" goes beyond military means as a way to implement politics (or policy). In contrast, [military] strategy is the highest level of how to structure and deploy a nation's military forces. It must first deal with the strength, composition, and capabilities of those forces, and then decide on a command structure, which is often based on geographic areas of operations, and often domestic or military politics. For example, a basic Allied strategic decision in the Second World War was to divide operations into European, Pacific, and Mediterranean, but, in the Pacific, it was necessary to divide into Southwest Pacific and Pacific Ocean areas. The necessity came from the need to manage the notable ego and skills of Douglas MacArthur.

Operational art

Operational art is a relatively new term, between tactics and strategy. If strategy defines one's areas of operations, operational art defines the priorities and campaigns withi the various areas. A master of operational art sets conditions such that battles happen at the places, times, and other circumstances that give maximum advantage to one's side. The term "preparation of the battleground", or, in more recent jargon, "preparation of the battlespace", applies here.

Tactics

Tactics deal with how those battles are fought. Unfortunately, the term deals with levels of fighting with organizations ranging from divisions of 25,000 soldiers down to fire teams of 3-5 soldiers.